April, igo6.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



417 



diiced by Oberhauser, certainly before 1857. It was 

 not received with favour in this country as it was con- 

 sidered that too much work had to be done by the 

 ocular in comparison with that required in the Eng^lish 

 form, that is, to obtain the same amplification. Con- 

 sequent on the great improvements by .•\bbe in the 

 construction of objectives, this objection cannot now 

 be sustained, as a modern objective should stand such 

 majrnification by the ocular as Vi-ill bring- the total 

 amplification up to one thousand times the N.A., with- 

 out furnishing a " rotten " image. For ease of ob- 

 servation when the instrument is placed in a vertical 

 position, as, for instance, when using fluid media on 

 the stage, the advantage of the short-tube form is in- 

 disputable. In photomicrography the long-tube has 

 some advantages, but the ideal instrument was con- 

 sidered to be a short-tube stand, which could be quickly 

 converted to the long form, cither tube length being 

 available as required. 



Cinematograph and Microscopy. 



At a recent meeting of the Society of Art?, Mr. F. M. 

 Duncan showed examples of the successful application 

 of the cinematograph to microscopical investigation, 

 illustrating the circulation and rotation of protoplasm., 

 and the movement of the chlorophyll bodies within the 

 cells of the leaf of Elodca; the circulation of the blood 

 in the web of the frog's foot and in the tail of the gold- 

 fish. The lecturer also exhibited micro-bioscope pictures 

 of Hydra Viridis. various birds, beasts, and reptiles in 

 motion, and of the life and work of the wood ant. 



Notes and Queries. 



S. C. Mitra, Bombay. — The samples of wood sent you con- 

 tain various woods, but yon will find drawings in Hertzberg's 

 book which will enable you to judge of this for yourself. 1 he 

 colours of the wood-pulps mean merely that one is treated 50 

 as to be of a whiter colour for paper-making and to need less 

 bleaching. Some wood fibres polarize very well, others not at all 

 — it is largely a matter of treatment in manufacture. A thin 

 slice of raw deal, for instance, polarizes excellently. Polar- 

 ized light often brings the structure out better, but not always 

 — it is of course a question of refraction. 



C. E. Garner, Shan^Iiai. — I was glad to get your letter and 

 wish you all success with your work. It must be very difficult 

 to work so far from home, but I shall be very glad to help you 

 in any way I can. You certainly have a good outfit and no 

 lack of books of reference. You cannot do better than con- 

 tinue your entomological studies, and I should be most grate- 

 ful for any insects you can send me, many of which would 

 very probably be welcome in the University Museum 

 here. The mere collecting of insects from your district for 

 transmission home would be of much interest and use, with 

 such additional study as you could give them. Do you ever 

 get any mites ? I kno v at least two people here to whom they 

 would be of great interest. 



ir. IL. M., Tunbridijc U'cUs. The best monochromatic 

 liglu is undoubtedly obt;iineil with a prism ;in(l heliostat, but 

 this has such pal|)able disadvantages that it is X'kloni used. 

 The prism has recently been adapted for use with a Nernsl 

 electric lamp, and this gives very good results, but with any 

 less powerful means- of illumination the loss of light is 

 too great. For all ot'dinary purposes, Mr. GilTord's new 

 fluid sprceil fulfils. every requirement. It consists of a slip 

 of signal green glass immersed in a solution of malachite 

 lirecn in glycerine, and gives practically monochromatic 

 light, though even here there is a niarkeil loss of light 

 when using immersion lenses. Mr. tiilTord's .simple little 

 F line screen, which drops into the condenser mount is 

 cheap and bandy, but I(":s perfect, .-ind loses more light still. 

 I b;ive found lli<' lluiil screen fullil everv requirenn'rU. 



" Arabian," Jerusalem. — I do not consider that there is 

 any difference in workmanship in the two microscopes you 

 mention, in spite of the difference in price. You are, how- 

 ever, quite right in your criticisms as to the Continental 

 form of fine adjustment, and though makers who used this 

 adjustment for a long lime argued stoutly that it was not 

 unsatisfactory, they have now admitted it by fitting im- 

 proved adjustments to their more expensive stands, such as 

 you mention. These adjustments are a great improvement, 

 but they are expensive. My advice would certainly be to 

 have this improved fine adjustment if you have definitely 

 decided to buy a Continental stand, but an English stand, 

 it carefully selected, would be equally satisfactory in every 

 way and would, contrary to the common idea, cost you less. 

 [between the two immersion lenses you mention there is, in 

 my opinion, nothing lo choose. Both are excellent. 



2?. S. B. P., Sfreatliam. — Mr. Cole's method of mounting 

 pollen is, after drying it, to soak it for some days in turpen- 

 tine, and then to mount the cover-glass in a drop or two 

 of Canada balsam, spreading the grains evenly with a 

 needle, and then putting away to dry. When drv, it is 

 only necessary to add another drop or two of balsam, and 

 to mount on a warm slide in the usual way. Bv this means 

 the pollen is prevented from running together in the centre 

 of the slide. Pollen makes beautiful opaque mounts. 

 Pollens can be stained readily by any of the aniline dyes, 

 such as methyl blue or green. They must be first soaked 

 in methylated spirit to remove air and colour, then dved in 

 a strong' alcoholic solution of the stain for an hour or two ; 

 the stain poured off, rinsed in spirit, this poured awav and 

 clove oil added ; this aeain poured away, and mounting in 

 Canada balsam proceeded with as above. V'ery pretty 

 slides can be made by staining equal quantities of the pollen 

 different colours and mixing them together just before 

 mounting in the Canada balsam. Gentian violet and 

 Vesuvin are bacterial stains, and the former is also used 

 as a general nuclear stain. 



A. G., ChorUon-cum-Tlardy . — It is not very easy to answer 

 your questions. The amount of mathematics required " to 

 study light " depends upon how far you wish to go in your 

 study, and I should scarcely advise a man to study the sub- 

 ject from its mathematical side who had not a good pre- 

 liminarv grounding in algebra, geometry, and trigonometry, 

 as a basis. Perhaps the best book on algebra for a home 

 student would be Hall and Knight's " Elementary 

 .Mgebra," and it would be necessary to know practically the 

 whole of this book as well as such an elementary book on 

 Trigonometry as Lock's. In the same way it is not easy 

 to say how much Euclid is necessary. \Vhat is really 

 necessary is a sound preliminary mathematical training, and 

 for this the whole of Euclid cannot be considered too much. 

 On the other hand, if you merely wish to understand and 

 follow such simple mathematical expressions as would be 

 found, for instance, in tdazebrook's " Light," I suppose a 

 knowledge of .algebraical addition, subtraction, multiplica- 

 tion, and division, and of simple equations, would serve 

 your purpose. 



H. P. M., London. — I am sorry your questions have re- 

 mained so long unanswered, but it has been due to the 

 necessity of getting your specimens named, for which I am 

 indebted to the kindness of Mr. E. R. Burdon, the Curator 

 of the Botanical Museum in the I'niversity of Cambridge. 

 He savs : " The bright reddish-pink cushions on a bit of 

 bark are fructifications of Nectria ; the waxy darker coloured 

 pustules on a bit of wood are Dacryomyces ; the brown 

 pustules on birch bark are some species of Hvpo- 

 .\ylon. .Ml these are fungi. The withered piece of a fruit 

 had two oblong brown bodies, which have got knocked olT, 

 but I think they were cocoons or eggs of .some insect. The 

 circular patches on the back of a bit of a fern frond arc 

 groups (' sori ') of sporangia of the fern .Vspidium. I am 

 afraid there is no book of a popular nature on the smaller 

 fungi tother than Cooke's). The only way to identify 

 such fungi is to cut sections and see the nature of the 

 fructifications and size and colour of the spores— and then, in 

 most cases, ask an expert." 



[Commiiniiiitioiis and Enquiries on Mierosecfieal nutlters should he 

 addressed t> F. Sliilli'igton Scales. ••Jersey," St. Bartiabiis Road, 

 Cambridge.] 



